Revert 253c922: restore the PM/RBAC work to the integration

Reverting the production revert so the pm branch can merge cleanly on
top of the restored RBAC base. Conflicts against newer integration work
resolved by combining:
- App.tsx: v7's bot-draft wizard bypass + login returnUrl kept alongside
  the supervisor gating (no-project block screen, panel scoping)
- LoginPage: returnUrl navigation kept, supervisor routing added
- migration.sql: bot_drafts table kept, unified-projects ALTERs restored

backend/app/routers/line_items.py

@@ -3,6 +3,7 @@ from fastapi import APIRouter, Depends, Query
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from app.auth import require_role
 from app.db.engine import get_db
 from app.models.catalog import Material, Unit
 from app.models.procurement import ItemDecision, LineItem, Quote
@@ -14,6 +15,7 @@ from app.utils.errors import ConflictError, NotFoundError
 from app.utils.pagination import paginate, sort_query
 
 router = APIRouter(prefix="/quotes/{quote_id}/line-items", tags=["line-items"])
+_procurement_writer = require_role("admin", "procurement_manager")
 
 
 async def _quote_or_404(db: AsyncSession, quote_id) -> Quote:
@@ -50,7 +52,12 @@ async def list_line_items(
 
 
 @router.post("", status_code=201)
-async def create_line_item(quote_id, payload: LineItemCreate, db: AsyncSession = Depends(get_db)):
+async def create_line_item(
+    quote_id,
+    payload: LineItemCreate,
+    db: AsyncSession = Depends(get_db),
+    _auth=Depends(_procurement_writer),
+):
     async with db.begin():
         quote = await _quote_or_404(db, quote_id)
         if quote.status != "offered":
@@ -89,7 +96,11 @@ async def get_line_item(
 
 @router.patch("/{line_item_id}")
 async def update_line_item(
-    quote_id, line_item_id, payload: LineItemUpdate, db: AsyncSession = Depends(get_db)
+    quote_id,
+    line_item_id,
+    payload: LineItemUpdate,
+    db: AsyncSession = Depends(get_db),
+    _auth=Depends(_procurement_writer),
 ):
     li = await _line_item_or_404(db, quote_id, line_item_id)
     quote = await _quote_or_404(db, quote_id)
@@ -131,7 +142,12 @@ async def update_line_item(
 
 
 @router.delete("/{line_item_id}")
-async def delete_line_item(quote_id, line_item_id, db: AsyncSession = Depends(get_db)):
+async def delete_line_item(
+    quote_id,
+    line_item_id,
+    db: AsyncSession = Depends(get_db),
+    _auth=Depends(_procurement_writer),
+):
     li = await _line_item_or_404(db, quote_id, line_item_id)
     quote = await _quote_or_404(db, quote_id)
     if quote.status != "offered":